1. Field of the Invention
The present invention relates to an electrically operable toothbrush, in particular an electrically operable toothbrush which includes an oscillatingly rotatable brush head, with the brush head being connected with a drive shaft, so as to be supported for rotation about its longitudinal axis. An electric motor is arranged in a handgrip of the toothbrush and a gearing having the input thereof connected with the electric motor and the output thereof with the drive shaft.
Electrical toothbrushes of that type are already widely employed in the practice and known from the literature. These toothbrushes consist, in general, of a handgrip in which there is located a storage battery, an electric motor and a gearing or power transmission which has an input connected with the electric motor. The gearing drives a drive shaft which is usually arranged so as to extend in parallel with the longitudinal axis of the elongate handgrip, and conducted outwardly from the upper and of the handgrip. Mountable on the drive shaft is a brush attachment which, in general, is exchangeable in nature.
The brush attachment, in turn, possesses a drive shaft which is directly connected with the drive shaft in the handgrip, so as to form an extended drive shaft. Furthermore, the brush attachment is equipped with a brush head, which is supported in a manner so as to be able to implement oscillatory rotational movements. The brush head is coupled with the drive shaft through the intermediary of a reversing mechanism. Hereby, the brush head is mostly orientated such that its central axis extends somewhat perpendicular to the longitudinal axis of the drive shafts. However, there also exist toothbrushes whose brush heads possess a central axis which is oriented in parallel with the longitudinal axis of the drive shafts.
2. Discussion of the Prior Art
An electrically operable toothbrush of that type, for example, is disclosed in German DE 39 37 854 A1. The toothbrush which is disclosed therein possesses essentially some of the basic features of the above-mentioned toothbrush construction. In particular, this known electrically operable toothbrush possesses an electric motor which is arranged in a handgrip, which motor through the interposition of a gearing device and a reversing mechanism actuated by the latter oscillatingly drives a rotatably supported brush head. The gearing device is constructed as a quadrilateral control linkage system which, at the input thereof, is driven through a spur gear arrangement by the electric motor, and at the output end thereof oscillatingly drives a drive shaft within angular range of about xc2x135xc2x0.
In addition to these known toothbrushes with oscillatingly rotatable brush heads, there also exist toothbrushes with brush heads which carry out swinging or pendulous movements, or also which superimpose two oscillatory movements. Toothbrushes of that type in general require a completely differently constructed gearing device in order to produce these brush head movements.
Accordingly, proceeding from the above-mentioned state-of-the-technology, it is an object of the present invention to provide an electrically operable toothbrush with an oscillatingly rotatable brush head which operates at an extremely high degree of efficiency, and the gearing drive, of which is almost noiseless during its operation.
The foregoing object is obtained through the provision of an electrically operable toothbrush in which the transmission or gearing has a first eccentric wheel positioned on a gear shaft which is essentially arranged perpendicular to the drive shaft, a second eccentric wheel positioned on the shaft, and a drive wheel which is coupled to the first and second eccentric wheels, wherein the first eccentric wheel is arranged in a circular recess in a holder for the drive shaft so as to be able to displace the drive shaft upwardly and downwardly, and wherein the second eccentric wheel is arranged in an oval recess in the holder in order to stabilize the lift or the stroke of the drive shaft.
The gearing which is employed in the inventive toothbrush as described above facilitates that on the one hand, there is obtained an extremely high degree of operating efficiency for the transmission or gearing, in effect, almost the total energy introduced from the electric motor is converted into the lift or stroke of the drive shaft, while moreover, this gearing operates almost noiselessly.
Advantageously, the first and second eccentric wheels are fastened in such a manner on the driving mechanism shaft, such that their eccentricities with regard to the driving mechanism shaft are oriented directly oppositely, whereby the eccentricity of the first eccentric wheel is greater than that of the second eccentric wheel so that the lift or stroke of the drive shaft is defined by the sum of the eccentricities of two eccentric wheels with regard to the driving mechanism.
Furthermore, it is advantageous to guide the drive shaft through the intermediary of one or more ball bearings located interiorly of the handgrip. Due to the lubricating effect of the ball bearings, there can be reduced any frictional, overheating and wear effects acting on the drive shaft.